Update #0 - First Release

sources/main/java/com/google/common/hash/Murmur3_32HashFunction.java

@@ -0,0 +1,190 @@
+/*
+ * Copyright (C) 2011 The Guava Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+/*
+ * MurmurHash3 was written by Austin Appleby, and is placed in the public
+ * domain. The author hereby disclaims copyright to this source code.
+ */
+
+/*
+ * Source:
+ * http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp
+ * (Modified to adapt to Guava coding conventions and to use the HashFunction interface)
+ */
+
+package com.google.common.hash;
+
+import static com.google.common.primitives.UnsignedBytes.toInt;
+
+import java.io.Serializable;
+import java.nio.ByteBuffer;
+
+import javax.annotation.Nullable;
+
+import com.google.common.primitives.Chars;
+import com.google.common.primitives.Ints;
+import com.google.common.primitives.Longs;
+
+/**
+ * See http://smhasher.googlecode.com/svn/trunk/MurmurHash3.cpp
+ * MurmurHash3_x86_32
+ *
+ * @author Austin Appleby
+ * @author Dimitris Andreou
+ * @author Kurt Alfred Kluever
+ */
+final class Murmur3_32HashFunction extends AbstractStreamingHashFunction implements Serializable {
+	private static final int C1 = 0xcc9e2d51;
+	private static final int C2 = 0x1b873593;
+
+	private final int seed;
+
+	Murmur3_32HashFunction(int seed) {
+		this.seed = seed;
+	}
+
+	@Override
+	public int bits() {
+		return 32;
+	}
+
+	@Override
+	public Hasher newHasher() {
+		return new Murmur3_32Hasher(seed);
+	}
+
+	@Override
+	public String toString() {
+		return "Hashing.murmur3_32(" + seed + ")";
+	}
+
+	@Override
+	public boolean equals(@Nullable Object object) {
+		if (object instanceof Murmur3_32HashFunction) {
+			Murmur3_32HashFunction other = (Murmur3_32HashFunction) object;
+			return seed == other.seed;
+		}
+		return false;
+	}
+
+	@Override
+	public int hashCode() {
+		return getClass().hashCode() ^ seed;
+	}
+
+	@Override
+	public HashCode hashInt(int input) {
+		int k1 = mixK1(input);
+		int h1 = mixH1(seed, k1);
+
+		return fmix(h1, Ints.BYTES);
+	}
+
+	@Override
+	public HashCode hashLong(long input) {
+		int low = (int) input;
+		int high = (int) (input >>> 32);
+
+		int k1 = mixK1(low);
+		int h1 = mixH1(seed, k1);
+
+		k1 = mixK1(high);
+		h1 = mixH1(h1, k1);
+
+		return fmix(h1, Longs.BYTES);
+	}
+
+	// TODO(user): Maybe implement #hashBytes instead?
+	@Override
+	public HashCode hashUnencodedChars(CharSequence input) {
+		int h1 = seed;
+
+		// step through the CharSequence 2 chars at a time
+		for (int i = 1; i < input.length(); i += 2) {
+			int k1 = input.charAt(i - 1) | (input.charAt(i) << 16);
+			k1 = mixK1(k1);
+			h1 = mixH1(h1, k1);
+		}
+
+		// deal with any remaining characters
+		if ((input.length() & 1) == 1) {
+			int k1 = input.charAt(input.length() - 1);
+			k1 = mixK1(k1);
+			h1 ^= k1;
+		}
+
+		return fmix(h1, Chars.BYTES * input.length());
+	}
+
+	private static int mixK1(int k1) {
+		k1 *= C1;
+		k1 = Integer.rotateLeft(k1, 15);
+		k1 *= C2;
+		return k1;
+	}
+
+	private static int mixH1(int h1, int k1) {
+		h1 ^= k1;
+		h1 = Integer.rotateLeft(h1, 13);
+		h1 = h1 * 5 + 0xe6546b64;
+		return h1;
+	}
+
+	// Finalization mix - force all bits of a hash block to avalanche
+	private static HashCode fmix(int h1, int length) {
+		h1 ^= length;
+		h1 ^= h1 >>> 16;
+		h1 *= 0x85ebca6b;
+		h1 ^= h1 >>> 13;
+		h1 *= 0xc2b2ae35;
+		h1 ^= h1 >>> 16;
+		return HashCode.fromInt(h1);
+	}
+
+	private static final class Murmur3_32Hasher extends AbstractStreamingHasher {
+		private static final int CHUNK_SIZE = 4;
+		private int h1;
+		private int length;
+
+		Murmur3_32Hasher(int seed) {
+			super(CHUNK_SIZE);
+			this.h1 = seed;
+			this.length = 0;
+		}
+
+		@Override
+		protected void process(ByteBuffer bb) {
+			int k1 = Murmur3_32HashFunction.mixK1(bb.getInt());
+			h1 = Murmur3_32HashFunction.mixH1(h1, k1);
+			length += CHUNK_SIZE;
+		}
+
+		@Override
+		protected void processRemaining(ByteBuffer bb) {
+			length += bb.remaining();
+			int k1 = 0;
+			for (int i = 0; bb.hasRemaining(); i += 8) {
+				k1 ^= toInt(bb.get()) << i;
+			}
+			h1 ^= Murmur3_32HashFunction.mixK1(k1);
+		}
+
+		@Override
+		public HashCode makeHash() {
+			return Murmur3_32HashFunction.fmix(h1, length);
+		}
+	}
+
+	private static final long serialVersionUID = 0L;
+}